Prior art methods for the stabilization of polyalkylene polyether polyols with antioxidants or stabilizers and the use of stabilized polyols in the preparation of polyurethane foams to inhibit scorch are well known. Polyether polyols, used in the manufacture of slabstock flexible urethane foam, are typically stabilized with antioxidant packages consisting of phenolic and amine antioxidants, and may also contain the synergist phenothiazine.
U.S. Pat. Nos. 3,567,664 and 3,637,865 disclose polyurethane foams stabilized with a mixture of 2,6-di-tert-butyl-4-methyl phenol [butylated hydroxy toluene (BHT)] and p,p'-dialkyldiphenylamines. U.S. Pat. No. 4,010,211 teaches the addition of phenothiazine to a BHT/p,p'-dialkyldiphenylamine mixture. U.S. Pat. No. 4,794,126 discloses flame-retardant polyurethane foams stabilized with a combination of a diarylarylenediamine, a reaction product of diarylamine and alkyl ketone and a hindered phenol, specifically 3,6'-di-tert-butyl-4-sec-butyl phenol.
U.S. Pat. No. 4,933,374 discloses polyoxyalkylene polyether polyol compositions protected against oxidative degradation with a stabilizing amount of a synergistic mixture of 2,6-di-tert-butyl-4-sec-butyl phenol and a reaction product of diisobutylene, styrene, and diphenylamine wherein the weight ratio of the diisobutylene to the styrene is from about 2:1 to 5:1.
U.S. Pat. No. 4,551,493 is concerned with transparent flame-retardant poly(arylether-arylsulfone) molding materials. An example of a heat stabilizer given is a hindered phenol and a diphenylamine/acetone condensate. In this patent, the final product is used as a flameproofing agent for plastic molding materials. Certain simple acridan compounds of the instant invention are disclosed but not exemplified as useful in stabilization of the sulfur bearing poly (aryletherarylsulfone) polymers. Furthermore, the cyclic or linear diphenylamine/acetone condensate of U.S. Pat. No. 4,551,493 are used in combination with a poly(2,6-dibromophenylene 1,4-oxide). The compositions of the instant invention are not halogenated in any manner nor do the stabilized polymer chains contain a sulfur linkage.
Antioxidants are used in polyether polyols to protect the polyol from oxidation during the final stages of manufacture; to reduce peroxide formation during storage; and to reduce the possibility of scorching the flexible polyurethane slabstock foam due to thermal oxidative degradation.
The compounds of this invention are particularly important to the polyol/flexible urethane industry due to the increased concern over chlorofluorocarbons (CFCs) and their deleterious effect on the earth's ozone layer. CFCs are incorporated in flexible slabstock foam to serve as an auxiliary blowing agent and for the removal of heat during slabstock production. The absence of CFCs places a higher performance requirement on the stabilization system, since the CFCs prevent discoloration, physical scorch and self-ignition of the foam.
The presence of scorch is of major concern to the foam manufacturers since it negatively affects the appearance of the product, causes physical damage and may result in fire. Recent regulations eliminating the use of CFCs in polyurethane foam manufacture require enhanced scorch protection during flexible slabstock foam production.
It would therefore be advantageous to have a antioxidant system for polyether polyol stabilization that provide increased scorch protection, allow foams to be produced at higher internal temperatures, and eliminate the use of CFCs without adverse effects to the foam.
Accordingly, it is an object of this invention to provide a stabilizer system for polyether polyols which provides valuable protection for oxidation, scorching, and discoloration of resultant foam produced, including those foams produced containing flame retardants.
It is a further object of this invention to provide an environmentally friendly stabilization package for polyether polyols. More specifically, a stabilization package which holds the possibility of eliminating the need for chlorofluorocarbons, heretofore used in flexible polyurethane foam production.
It is a still further object of this invention to provide a flexible polyurethane foam product made from the stabilized polyol together with an isocyanate with improved scorch performance, appearance, and color.
The foregoing and additional objects will become more evident from the following description and Examples.